When such conditions arise on the PGA Tour, the tour invokes a rule that allows the player to lift and clean his ball if it rests in the fairway, and then place it back where it was. However, the U.S. Golf Association allows for no such rule and requires the ball to be played as it lies.
And players fear that a mud ball going 30 to 40 yards off line in the direction opposite the mud mark on the ball - i.e. mud on the left half, ball squirts to the right - could be disastrous for a leader coming down the stretch on Sunday.
"Mud takes spin off, so it doesn't take much mud to really affect the ball," veteran Steve Stricker said. "It's unfortunate, but we're going to have to deal with it, I think. And yeah, it could decide who the champion is here this week, unfortunately.
"It's just golf, I guess. We've got to deal with it even though we're not going to be happy about it."
Tiger Woods, who is seeking his fourth U.S. Open championship and first major in five years, said the mud balls will be "interesting."
"The shorter holes, if you catch a ball that's got a little bit of mud on it, you can't be as precise," Woods said.
Another factor for players is controlling the spin of their wedges and short irons. The rain-softened greens will be more receptive to well-struck shots, but the ball could spin violently away from the hole if the contestant is not careful.
"The greens are soft and fast, which is a bad combination for tour players," said Graeme McDowell, the 2010 U.S. Open champion at Pebble Beach. "We'll spend the week trying to take the spin off wedges. You'll see guys over the back of the greens to the back pins in massive trouble."
One more concern is the weather forecast for Thursday: heavy rain and wind similar to what was seen Friday and Monday. More water on the course would mean a possible suspension of play, and even with good conditions forecast for the final three days, the likelihood that the course will not firm up before the conclusion of the championship.
"The golf course is going to be obviously wet out there, hopefully with a chance to dry out somewhat before the weekend," McDowell said. "But it's got a lot of drying-out to do, and possibly we will be playing a fairly wet golf course for the rest of the week."
Contact Joe Juliano at email@example.com. Follow on Twitter @JoeJulesInq.